It is well known in the art that N,N-dimethyl formamide (DMF) is an efficient selective solvent to remove, e.g., acetylenes from gas streams containing such acetylenes in addition to olefins. One of the problems occurring in such an absorption process is that a small portion of the dimethyl formamide leaves the absorption zone overhead together with the deacetylenized gas. It already has been proposed to remove entrained selective solvent by contacting the absorber overhead gas stream raffinate with liquid ethylene. This procedure, generally applied to the removal of acetylene (C.sub.2 H.sub.2) from ethylene (C.sub.2 H.sub.4), which can basically be characterized as refluxing the absorption column with liquefied ethylene overhead gas, is fairly complicated and expensive because ethylene must be first liquefied and fed to the column with precise control to prevent substantial loss in the rich DMF kettle product from which the acetylenes are later stripped. If a separate contacting unit is utilized, as has been proposed in the art, the ethylene/dimethyl formamide mixture must later be separated so that a plurality of units is then required, which adds to the overall cost of the process and may render it economically unattractive.
It would thus be desirable to have a process available by which the expensive dimethyl formamide solvent leaving the dimethyl formamide absorber overhead with the product gas is readily and relatively inexpensively recovered.
Furthermore, it is known in the prior art that such commercially available gas streams as coke oven gas contain sulfur compounds such as H.sub.2 S, COS and CS.sub.2. These low-boiling sulfur compounds are very undesirable and need to be removed to prepare suitable feedstock for processes utilizing such gases. Thus it would be desirable to have a process available by which the sulfur compounds in gases such as coke oven gas can be readily removed as well.